A Randomized Controlled Trial of PCIT-ED for Preschool Depression Data from several independent research groups have demonstrated that the onset of DSM-IV depressive disorders may occur as early as the preschool period. A stable and specific symptom constellation, family history of related disorders, characteristic alterations in stress cortisol reactivity as well as homotypic continuity with depression at school age provide strong support for the principle that preschool depression represents an early onset form of the later childhood disorder. Epidemiological studies from both U.S. and European sites estimate the prevalence rate of preschool onset depression (PO-MDD) at 1-2%, the same rate found in school- aged children. New data from our lab suggest that depressed preschoolers display alterations in functional brain activity similar to that found in adult depression. These brain changes were detected both during an acute preschool episode and later at school age, even after the depressive episode remitted. These findings taken together underscore the need for treatment of MDD during the preschool period. However, because PO-MDD has only recently been recognized, investigations of treatments remain uncharted. The need for effective treatments for PO-MDD go beyond the important goal of helping affected preschoolers but may also have implications for earlier and potentially more effective interventions in this chronic and relapsing disorder. Based on the large effect sizes reported in early interventions in several preschool disorders, an early intervention for PO-MDD, Parent Child Interaction Therapy Emotion Development (PCIT-ED) was developed and pilot tested. PCIT-ED is an expansion of PCIT, a well-known, widely used and proven effective treatment for preschool disruptive disorders. To address early disturbances of mood and affect, a novel ED module was added based on empirical data in emotion development. The ED module targets parent emotion learning skills with the goal of training the parent to serve as a more effective emotion teacher and coach to the child. The goal of the ED module is to enhance the child's capacity for emotion recognition and regulation or emotional competence. A pilot randomized controlled trial of PCIT-ED was conducted demonstrating feasibility and promise of efficacy. Following these findings, this application proposes a large scale well powered RCT of PCIT-ED for PO-MDD compared to a wait list control after which subjects will receive the active treatment. The aim is to rigorously test the efficacy of PCIT-ED, to estimate accurate effect sizes and to investigate mediators and moderators of treatment response.